Detrainment and braking of snow avalanches interacting with forests

Abstract

Abstract. Mountain forests provide natural protection against avalanches. They can both prevent avalanche formation in release zones and reduce avalanche mobility in runout areas. Although the braking effect of forests has been previously explored through global statistical analyses on documented avalanches, little is known about the mechanism of snow detrainment in forests for small and medium avalanches. In this study, we investigate the detrainment and braking of snow avalanches in forested terrain, by performing three-dimensional simulations using the material point method (MPM) and a large-strain elastoplastic snow constitutive model based on critical state soil mechanics. First, the snow internal friction is evaluated using existing field measurements based on the detrainment mass, showing the feasibility of the numerical framework and offering a reference case for further exploration of different snow types. Then, we systematically investigate the influence of snow properties and forest parameters on avalanche characteristics. Our results suggest that for both the cold and warm snow parameterized in our simulations, the detrainment mass decreases with the square of the avalanche front velocity before it reaches a plateau value. Furthermore, the detrainment mass significantly depends on snow properties. It can be as much as 10 times larger for warm snow compared to cold snow. By examining the effect of forest configurations, it is found that forest density and tree diameter have cubic and square relations with the detrainment mass, respectively. The outcomes of this study may contribute to the development of improved formulations of avalanche–forest interaction models in popular operational simulation tools and thus improve hazard assessment for alpine geophysical mass flows in forested terrain.

Diachronic quantitative snow avalanche risk assessment as a function of forest cover changes

“…This sounds generally true, except when more forest leads to a higher incorporation of trunks within avalanche flows that can generate high impact pressures, and, hence, potentially increase the risk to buildings and people inside. These different shortcuts could potentially be relaxed in future developments, notably by including more advanced numerical modeling techniques within the workflow to represent the complex interactions between avalanche flows, forest stands and buildings (Védrine and others, 2021). However, a computational effort much higher than the one required to implement our approach would then be necessary.…”

“…More recently, as an alternative to frictional approaches, Feistl and others (2014) proposed the detrainment approach in which the forest–avalanche interaction is modeled through a single-parameter detrainment function. This approach accounts for the braking effect of forests on avalanche flows, and has been recently implemented in most up-to-date snow avalanche simulation models (Védrine and others, 2021).…”

The potential of non-native tree species to provide major ecosystem services in Austrian forests

“…Steep alpine terrains, which are frequently occurring in the Alpine South zone in Austria ( Figure 1C ) are susceptible to hazards like avalanches, rockfalls, and mudflows ( Fischer et al., 2012 ). Alpine forests ( Figure 1B ) play a crucial role as natural barriers, safeguarding settlements and infrastructure by slowing down and containing avalanches ( Bebi et al., 2009 ; Védrine et al., 2022 ). The intricate root network of these forests further prevents soil erosion, offering protection against rockfall and mudflows ( Dorren and Schwarz, 2016 ).…”

Debris flow: Simulating the mitigation properties of vegetation

“…* Corresponding author: alessandro.leonardi.ing@gmail.com; a.leonardi@sheffield.ac.uk It is difficult to quantify the mitigation effectiveness of any design than involves vegetation. Preliminary studies have been conducted by Vedrine et al (2021) on snow avalanches [14], or Luong et al, (2020) on dry granular flows [15]. These studies have reported that vegetation can have a positive breaking effect, mobilizing friction and dispersing the flow laterally.…”